Smoke detecting apparatus



Filed Oct. 1, 1952 A ttorney United States Pate-nt O 2,731,874 SMOKE DETECTING APPARATUS Cyril Clifford Hall, Ealing, London, England, assigner to Specialties Development Corporation, Belleville, N. J., a corporation of New Jersey Application October 1, 1952, Serial No. 312,612 5 Claims. (Cl. 88-14) The present invention relates to smoke detecting apparatus and, in particular, to apparatus using optical detection of smoke.

Smoke detecting systems are commonly employed for keeping a check on conditions in the various compartments and holds of a ship or in factory workshops and store rooms. In such smoke detecting systems it is customary to withdraw air samples continuously from the space to be protected atnd pass them through the apparatus, the smoke particles being detected by light in the apparatus and may be observed visually r by electrical means responsive to a photo-electric cell.

The object of the present invention is to provide a simplified apparatus for the detection of smoke (or dust) in the air, which is easy to construct and which will readily disclose the presence of smoke in the air to the eye of an observer.

It is common experience that the very fine particles of smoke when illuminated present a characteristic appearance and are much finer than the ordinary dust particles, which are commonly found in the air, particularly in industrial buildings, so that an observer can dilferentiate between the appearance of smoke and dust.

According to the present invention apparatus for smoke detection comprises a casing defining a darkened chamber, entry means for an air sample into the chamber, means for illuminating particles in the air sample from outside the chamber and observation means in the casing, screened from the illuminating means, so that the light may be reilected from illuminated particles to the eye of an observer viewing the samples through the observation means.

The air sample is preferably introduced into the darkened casing through one or more transparent glass tubes, which pass through a lower light-proof casing in which a light source is located, and discharge into the bottom of the first casing. The light source serves to illumine the smoke particles passing through the light-proof casing and the light dispersed by them illuminates smoke particles which are directly visible to the eye of an observer.

In order that the invention may be more fully understood one example of a construction made in accordance with the invention is hereinafter more fully described with reference to the accompanying drawing.

The drawing shows a section of the apparatus which comprises an outer casing 1 defining a darkened chamber in which the inner surfaces of the chamber are blackened by means of a suitable matte black paint. In the middle of the cuter casing 1 is an inner casing 2, which is light proof and contains a pair of longitudinally extending strip lights 3. These strip lights are positioned close to a number of glass tubes 4, which extend both upwardly and downwardly out of the casing and are arranged in three rows. The upper ends 4 of the glass tubes extend a little above the top of the inner casing 2 and are masked either by metal masks 5 attached to the casing 2 or by simply painting over the outer surface with a paint coating (preferably matte nish black paint). The tubes 4 are each identified by a number painted on t'o the appropriate mask 5 or on to the tube itself where it is black painted. The

casing, by means of a motor-driven air pump (not shown) connected to the outlet tube 8.

By using multiple tubes, as herein, it is possible to take air samples simultaneously from many parts of a ship or building so that one observer may check the whole lot at' any instant.

These ilickers 9 are illuminated by the lamps 3 and are located in a clear portion of the tubes situated beneath the inner casing 2.

The purpose of the ickers is to indicate to an observer that air is being drawn through the diiferent tubes; the illuminated ickers, moving in the stream serve to do this.

So as not to distract the eye of the observer, the flickers are normally screened by a hinged ap which contacts an abutment 11' on the inner case 4 and is operated by means of a lever 12 external of the outer casing 1. The ickers are also viewed through a second inclined glass 14, which is screened from the iirst glass 6 by a partition 15 the of both glasses.

Thus in operation the first step in making the routine check by means of the apparatus is to check that the motor driven air pump and strip lights 3 are switched on. Then the flickers are to be checked to see that air is flowing properly through each of the tubes 4. After this the iickers are masked from observation by raising the hinged ap 10. The apparatus is then ready for the check of the air streams issuing from each of the tubes i for the presence of smoke. lf there is smoke in any of the air streams it will b e apparent when viewed through the viewing glass 6 from the light dispersed by the smoke particles in the air strean The smoke particles issuing from the top of the tube 4, through which smoke-contaminated air is drawn, are illuminated from a strip light 3, not by direct illumination, but rather by light dispersed by smoke particles still within the screened part of the tube. By further dispersion of this light by the issuing smoke particles the eye of the observer is informed of the presence of smoke.

I claim:

1. Apparatus for smoke detection comprising an outer casing defining a darkened chamber, an air outlet means from said chamber, a plurality of transparent tubes in said chamber, each of said tubes being adapted to be connected to an air line, an inner light-proof casing surrounding at least a portion of each of said tubes, at least one illuminating light source within said casing close to said tubes, the upper end of said tubes opening into the darkened chamber and means for viewing the inside of said darkened chamber screened from direct illumination from said light source.

2. Apparatus for smoke detection according to claim l illuminates each of the tubes in the row.

3. Apparatus for smoke detection comprising an outer casing having at least one viewing window therein, an inner casing within said outer casing, the interior surface of at least that part of said outer casing lying above said inner casing being darkened to form a darkened chamber, an air outlet in the top of said outer casing, a plurality of vertical transparent tubes supported in at least one row in said inner casing and opening into said darkened chamber, at least one horizontal strip light source arranged in said inner casing close to said tubes screened from directly illuminating the viewing window and means for connecting each of said tubes to an air line to draw an air sample from a distant compartment.

4. Apparatus for smoke detection comprising an outer casing having at least one viewing window therein, an inner casing within said outer casing, the interior surface of at least that part of said outer casing lying above said inner casing being darkened to form a darkened chamber, an air outlet in the top of said outer casing, a plurality of vertical transparent tubes supported in at least one row in said inner casing and opening into said darkened charnber, at least one horizontal strip light source arranged in said inner casing close to said tubes screened from directly illuminating the viewing window, means for con- 4. necting each of said tubes to an air line to draw an air sample from a distant compartment, a space below the inner casing between itself and the outer casing, said tubes having lower portions extending into said space, flicker members supported within said lower extending portions of said tubes and a movable screen to screen and unscrcen said icker members from an observation Window at will.

5. Apparatus according to claim 3, wherein said tubes project upwardly from said inner casing into said darkened chamber and said projecting portions are masked from observation from said window.

References Cited in the le of this patent UNITED STATES PATENTS 

1. APPARATUS FOR SMOKE DETECTION COMPRISING AN OUTER CASING DEFINING A DARKENED CHAMBER, AN AIR OUTLET MEANS FROM SAID CHAMBER, A PLURALITY OF TRANSPARENT TUBES IN SAID CHAMBER, EACH OF SAID TUBES BEING ADAPTED TO BE CONNECTED TO AN AIR LINE, AN INNER LIGHT-PROOF CASING SURROUNDING AT LEAST A PORTION OF EACH OF SAID TUBES, AT LEAST 